cluster: simplify process event handling
cluster: simplify process event handling

This simplify the internalMessage and exit event handling
And simply relay message and error event to the worker object
Note that the error event was not relayed before

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node